A TFIIH-associated mediator head is a basal factor of small nuclear spliced leader RNA gene transcription in early-diverged trypanosomes.

摘要: Genome annotation suggested that early-diverged kinetoplastids possess a reduced set of basal transcription factors. More recent work, however, on the lethal parasite Trypanosoma brucei identified extremely divergent orthologs TBP, TFIIA, TFIIB, and TFIIH which, together with small nuclear RNA-activating protein complex, form preinitiation complex (PIC) at spliced leader (SL) RNA gene (SLRNA) promoter. The SL is trans splicing substrate for maturation all pre-mRNAs which metabolized continuously to sustain expression. Here, we biochemically characterized novel TFIIH-associated in T. (Med-T) consisting nine subunits whose amino acid sequences are conserved only among kinetoplastid organisms. Functional analyses vivo vitro demonstrated essential cell viability, SLRNA transcription, PIC integrity. Molecular structure analysis purified Med-T Med-T/TFIIH complexes by electron microscopy revealed corresponds mediator head module higher eukaryotes. These data therefore show factor trypanosomes function characteristic feature eukaryotes developed early their evolution.